A US drone strike in southern Somalia has killed Adnan Garaar, a leader of the al-Shabaab militant group, the Pentagon said on Wednesday.

The March 12 strike hit a vehicle carrying Garaar, a top al Shabaab official suspected of masterminding the 2013 attack on the Westgate shopping mall in Nairobi that killed 67, the Pentagon said in a statement.

Al Shabaab is one of Africa’s largest and most powerful Al Qaeda affiliates. The group controls remote areas of southern Somalia and has pulled off deadly attacks in Kenya and Uganda as well.

The Westgate assault targeted a shopping mall in an upscale Nairobi neighbourhood, and is the group’s highest-profile external attack to date. The attack drew added international attention to the group, and about a year later, Ahmed Godane, Shabaab’s domineering leader, was killed in a US airstrike.

But Godane’s death hasn’t completely stopped Shabaab. Since then, the group has assassinated members of parliament, launched a deadly attack on a hotel in Mogadishu, and triggered a panic in the US over possible attacks on American shopping malls. The group’s operational capabilities — and its ability to spread fear — have remained intact. 

The drone strike on Garaar comes shortly after Nigeria’s Boko Haram pledged allegiance to ISIS , raising the spectre of a potential competition between ISIS and Al Qaeda for the loyalty of jihadist groups in Africa.